This invention relates to the removal of asbestos which has been applied for insulation and other purposes. Asbestos was used extensively for insulation in building construction and other purposes in the past. My invention also applies to removal of other hazardous particulate. Serious health hazards have now been associated with breathing particulate asbestos. Asbestos is being removed from many buildings where it was applied as part of wall finishes and insulation against heat transfer. Fibers 5 microns or greater in length and with an aspect ratio of 3:1 are addressed in environmental standards. A phase contrast optical microscope with about 440 magnification is used to count fibers. Requirements for an area to be undisturbed for 24 hours to allow fibers to settle does not provide for control of particulate matter in a work space where asbestos or other hazardous particulate matter is being removed. My invention does provide for control of particulate in a work space.
The description of my method and apparatus is directed to control asbestos particulates; however, my method and apparatus can be used to control other hazardous particulates.
Air filtration systems of many designs have been patented and others are available commercially. Vacuum flow collectors are available commercially. Vacuum flow collectors are in use to collect particulates such as graphite dust generated in performing machining operations on graphite work pieces. Filters then remove the particulates before the air is discharged to the outside.
U.S. Pat. No. 4,604,111 to Anthony Natale describes method and apparatus for controlling particulate matter in asbestos removal projects, for example: Natale provides an enclosed space, air flow establishing a negative air pressure, air flow entry, filtered air discharge, and seal of the air flow entry in case of the loss of the negative air pressure. Natale teaches the use of polyethylene plastic film flag seals to close air flow entryways to the contaminated work space.
A polyethylene plastic flap acting as a check valve allowing air flow through a doorway can be seen as not providing an effective seal of the doorway under condition of the loss of vacuum in the work space. Movement of contaminated air out of the work space can be expected even with low air flows caused by wind or artificial air circulation by adjacent air conditioning or ventilation blowers.
U.S. Pat. No. 2,710,574 to H. E. Runion describes a system for removing mist or particulates form an enclosure. U.S. Pat. No. 4,255,169 to R. M. Leliaert describes an energy conservation system of recirculating air to an industrial process with intermediate removal of dust or dirt. U.S. Pat. No. 4,175,934 to Arnold Lang discloses a "Clear Air Device" utilizing HEPA (High Efficiency Particulate Air) filtration to cleanse air for a positive pressure clean air room. U.S. Pat. No. 3,498,032, incorporated here by reference, describes a High Efficiency Particulate Air filter as covered by U.S. Federal Standard 209a.
A number of techniques have been developed to control particulate contamination during the removal of asbestos and other hazardous materials. Workers removing the hazardous materials need to be protected. Other people who must of necessity be near the work site need to be protected. For example, hazardous materials are to be removed from a portion of an airport terminal, hospital, or other site which needs to be in continued use.
It is the usual practice to establish and continue air circulation through a work space during the entirety of the decontamination process. If, however, there is a failure to continue the air circulation due to power failure or mechanical problem, the prior art does not teach effective method or apparatus to effectively seal the work space.
A long felt need exists to prevent escape of particulates from the work space at all times, even in the event of failure to continue air circulation during the decontamination process. In addition, a need exists for method and apparatus that is reasonably accomplished by decontamination workers with normal materials at hand.